Figure 6
Spatial variation of transforming growth factor beta (TGF-β) concentration within a perfused culture. The numerical solutions of Equations (5), (12) and (13) in Additional file 1 are shown for a 24-well-plate well of media height h 0 = 5 mm (corresponding to 1 ml culture) at day 8, for (a) Q = 0.5 ml/day, (b) Q = 1 ml/day and (c) Q = 2 ml/day. The diffusivity is D = 6.5 × 10−11 m2/second, the cell population is assumed constant at X = 105, and the secretion rate is r ϕ  = 1.94 × 10−6 pg/cell/day. Contours of TGF-β concentration are shown at the vertical mid-plane of the well.